From my limited reading the two most practiced forms of ratings are the Weight(Don Scott) ratings and the American Speed (Andrew Beyer) ratings.
Both types of ratings seem to rely on selecting a "base" run from which various factors are added/subtracted to develop a final rating.
Obviously if you don't select the horse's base run correctly all the extra adding and minusing are a waste of time.
Which brings me to the question to the ratings guys on the forum - which run do you use?
As an example I normally use the most recent run, except:
1. When the horse is first-up,
2. When the last run/s have been over unsuitable distances,
3. When the runs have been on rain-affected tracks,
etc,etc
In the end, is it sensible to be using just one run to base the ratings on, or should we be using some sort of weighted-average?
I doubt if there's a definitive answer but I'd love to know how other people tackle the problem.